In the coming year we will be concentrating our efforts to study: The phosphorylation of histone H5: (i) to perform pulse chase kinetic experiments to further investigate the observed under phosphorylation at the carboxyl-sites in the H5 from reticulocytes. (ii) to investigate the cell types responsible for this temporal variation in the sites of phosphorylation in H5. The metabolism of H5 in the chick/Hela heterokaryon as outlined in the original proposal. Photochemistry of Chromatin. (i) In view of the fact that U.V. irradiation is a sensitive probe to study the binding of histones to chromatin, we will ask if phosphorylated H5 binds to DNA with equal efficiency as unphosphorylated H5. (ii) To elucidate the binding site of histone H5 by purifying the U.V.- crosslinked peptides.